Abstract: A method is provided for determining the surface viscosity of a liquid in which a thread is formed from a drop of the liquid. The thread is lengthened and its minimum radius h0 is determined at multiple times between the thread formation and thread pinch-off. The minimum radius and associated time values are used to determine a linear relationship of minimum radius and time, with the coefficient of the linear relationship, or the slope X of the line in the linear relationship, corresponding to the surface viscosity ?s of the liquid according to one of the following equations: x = 0 . 0 ? 7 ? 0 ? 9 1 + 5 ? B s0 / 3 ? ? h 0 , ( 1 ) where Bs0=?s/?R in which h0 is defined as above, R is the dimension of the feature on which the drop is provided and ? is the bulk viscosity of the liquid, or x = 0 .